The present invention relates to an injection needle assembly used in combination with an endoscope.
Injection needle assemblies of this type comprise an elongate liquid feed tube made of resin and adapted to be inserted into an insertion channel of an endoscope. The tube has a needle at its distal end, and a connector at its proximal end. The connector can be coupled to an injector. The connector is a hollow cylinder, and a first metallic pipe is fixedly inserted in that end of the connector which is attached to the tube. One half of the first pipe projects from the connector. A second metallic pipe is fixedly inserted in the first pipe, with one end portion projecting from the first pipe. The projecting portion of the second pipe is fixedly inserted in the proximal end of the liquid feed tube.
To insert the injection needle assembly into the insertion channel of an endoscope, a stylet (wire) is inserted into the liquid feed tube through the connector to enhance the rigidity of the liquid feed tube to be inserted into a flexible sheath and then the needle assembly is inserted into the insertion channel together with the sheath.
As the stylet is inserted into the tube, however, it rubs the inner surface of the second pipe, producing metal dust. The first and second pipes are formed by cutting a very long pipe into pieces of a desired size. These pipes, however, are so narrow that the chips produced during the cutting remain in the pipes. When a medical fluid is injected into the body cavity through the injection needle assembly, it may mix with the metal dust or chips.
The first pipe is fastened to the connector by an adhesive, and the liquid feed tube is also fastened by an adhesive to the second pipe. The adhesive may flow into the pipes and the liquid feed tube. In such a case, the adhesive will hinder the insertion of the stylet. Furthermore, since the inner peripheral surface of the liquid feed tube is chemically treated for higher bonding strength, the dried treatment agent will possibly penetrate the liquid feed tube during the bonding work.